It's intended as recreation, yeah, but to me watching that video was like watching someone carry large rocks without aid of a wheelbarrow.

Or like digging a large ditch without aid of a backhoe.

To me there is a clear hierarchy or graduation of puzzles. Metaphorically:

1. Ditch digging by hand.

2. Planning efficient ditch layouts to be dug by machines.

3. Designing new and better ditch digging machines.

- - - -

1. Solving Sudoku puzzles.

2. Designing new Sudoku puzzles (with additional constraints even.)

3. Designing e.g. CLP(FD) programs to solve all sudoku puzzles everywhere.

- - - -

What I'm saying is, Why don't people move up that hierarchy? Why is level 1 so fascinating to people?

I believe that anyone who can solve sudoku can program a computer, but they don't. Why not?